Method for preparing granular polycrystalline silicon using fluidized bed reactor

Abstract

The present invention relates to a method for mass preparation of granular polycrystalline silicon in a fluidized bed reactor, comprising (a) a reactor tube, (b) a reactor shell encompassing the reactor tube, (c) an inner zone formed within the reactor tube, where a silicon particle bed is formed and silicon deposition occurs, and an outer zone formed in between the reactor shell and the reactor tube, which is maintained under an inert gas atmosphere, and (d) a controlling means to keep the pressure difference between the inner zone and the outer zone being maintained within the range of 0 to 1 bar, thereby capable of maintaining physical stability of the reactor tube and efficiently preparing granular polycrystalline silicon even at a relatively high reaction pressure.

1. A method for preparing polycrystalline silicon using a fluidized bed reactor, comprising:
 providing a fluidized bed reactor wherein a reactor tube is placed within a reactor shell so as to be encompassed by the reactor shell, whereby dividing an inner space of the reactor shell into an inner zone formed within the reactor tube and an outer zone formed in between the reactor shell and the reactor tube, wherein a silicon particle bed is formed and silicon deposition occurs in the inner zone while a silicon particle bed is not formed and silicon deposition does not occur in the outer zone; 
 maintaining a difference between an outer zone pressure (Po) and an inner zone pressure (Pi) at a condition of 0 bar≦(Pi−Po)≦1 bar wherein an inner pressure controller is spatially connected to the inner zone through at least one means selected from the group consisting of a fluidizing gas inlet means, a reaction gas inlet means, a silicon particle outlet means and an inner zone connecting means, which are spatially connected to the silicon particle bed; and 
 introducing an inert gas into the outer zone, whereby maintaining a substantially inert gas atmosphere in the outer zone. 
 
     
     
       2. The method of  claim 1 , further comprising measuring and/or controlling the inner zone pressure and measuring and/or controlling the outer zone pressure. 
     
     
       3. The method of  claim 1 , which further comprises introducing a fluidizing gas into the silicon particle bed, introducing a silicon atom-containing reaction gas into the silicon particle bed, heating the silicon particle bed, discharging polycrystalline silicon particles prepared within the inner zone to the outside of the fluidized bed reactor, and discharging an off-gas to the outside of the fluidized bed reactor, wherein a pressure difference between maximum pressure value and minimum pressure value in the silicon particle bed maintains from 0.01 bar to 1 bar. 
     
     
       4. The method of  claim 1 , wherein the reaction gas is a silicon atom-containing gas selected from the group consisting of monosilane, dichlorosilane, trichlorosilane, silicon tetrachloride and a mixture thereof. 
     
     
       5. The method of  claim 4 , wherein the reaction gas further comprises at least one gas selected from the group consisting of hydrogen, nitrogen, argon, helium, hydrogen chloride and a mixture thereof. 
     
     
       6. The method of  claim 1 , wherein the fluidizing gas is a gas selected from the group consisting of hydrogen, nitrogen, argon, helium, hydrogen chloride, silicon tetrachloride and a mixture thereof. 
     
     
       7. The method of  claim 1 , wherein the inert gas comprises at least one gas selected from the group consisting of hydrogen, nitrogen, argon and helium. 
     
     
       8. The method of  claim 1 , wherein the outer zone pressure (Po) or the inner zone pressure (Pi) maintains from 1 bar to 15 bar. 
     
     
       9. The method of  claim 1 , wherein the outer zone pressure (Po) is controlled in the range of between maximum and minimum pressure values measurable in the inner zone. 
     
     
       10. The method of  claim 1 , wherein at least one of the inner zone pressure (Pi) or the outer zone pressure (Po) is determined based on gas analysis of the gas that is present within or discharged out of the inner zone and/or the outer zone by using a gas analyzing part. 
     
     
       11. The method of  claim 3 , further comprising forming a packed bed of packing materials, which are not fluidized by the flow of the fluidizing gas in a lower part of the silicon particle bed with the height of the packed bed being positioned below a position where the reaction gas is introduced into the silicon particle bed. 
     
     
       12. A method for preparing polycrystalline silicon using a fluidized bed reactor, comprising:
 providing a fluidized bed reactor including an inner zone and an outer zone partitioned by a reactor shell and a reactor tube, wherein a silicon particle bed is disposed at a lower part of the inner zone; 
 introducing a fluidizing gas and a reaction gas into the silicon particle bed for a silicon deposition with an inner zone pressure (Pi) being maintained to be higher than an outer zone pressure (Po) at a condition of 0 bar≦(Pi−Po)≦1 bar wherein an inner pressure controller is spatially connected to the inner zone through at least one means selected from the group consisting of a fluidizing gas inlet means, a reaction gas inlet means, a silicon particle outlet means and an inner zone connecting means, which are spatially connected to the silicon particle bed; and 
 introducing an inert gas into the outer zone so as to maintain a substantially inert gas atmosphere in the outer zone. 
 
     
     
       13. The method of  claim 12 , wherein a pressure at an upper part of the inner zone is lower than an average pressure of the outer zone. 
     
     
       14. The method of  claim 12 , wherein the inner zone pressure (Pi) varies with a fluidization of the silicon particle bed, a pressure difference between a maximum pressure value and a minimum pressure value in the inner zone ranges from 0.01 bar to 1 bar.